Radial Evolution of Well-Observed Slow CMEs in the Distance Range 2 - 30 R _⊙

Abstract

We performed a detailed analysis of 27 slow coronal mass ejections (CMEs) whose heights were measured in at least 30 coronagraphic images and were characterized by a high quality index (≥4). Our primary aim was to study the radial evolution of these CMEs and their properties in the range 2 - 30 solar radii. The instantaneous speeds of CMEs were calculated by using successive height - time data pairs. The obtained speed - distance profiles [v(R)] are fitted by a power law v = a(R−b)^c. The power-law indices are found to be in the ranges a=30 - 386, b=1.95 - 3.92, and c=0.03 - 0.79. The power-law exponent c is found to be larger for slower and narrower CMEs. With the exception of two events that had approximately constant velocity, all events were accelerating. The majority of accelerating events shows a v(R) profile very similar to the solar-wind profile deduced by Sheeley et al. (Astrophys. J.484, 472, 1997). This indicates that the dynamics of most slow CMEs are dominated by the solar wind drag.